Railroad Archives Online
- ArquivoE0477 - BNSF Maps, Drawings and Records Collection
- Série003 - Great Northern Railway Company (U.S.)
- Subsérie009 - Engineering Records
- 005 - Signals
- 3 mais...
- ItemEBP3610 - Northern Pacific Signal Technical Drawing, 1898
- ItemEBP4365 - Great Northern Signal Technical Drawing, 1912
- ItemEBP4367 - Great Northern Signal Technical Drawing, 1918
- ItemEBP4368 - Great Northern Signal Technical Drawing, 1918
- ItemEBP4369 - Great Northern Signal Technical Drawing, 1918